In general, a compound resin material such as a plastic compound is manufactured by supplying a pellet or powder of a polymer resin serving as a base material into a barrel of an extruder or a continuous kneader together with an additive, and feeding the base material and the additive to the downstream side while kneading the base material and the additive with a kneading screw inserted into the barrel. A kneading degree of a material in the extruder and the continuous kneader is increased as the material remains in a kneading section in the barrel so that a kneading time is extended. Therefore, a kneading degree adjusting apparatus provided with a gate member for interrupting the material is provided on the downstream side of the kneading section in the extruder and the continuous kneader of the conventional art.
For example, the following Patent Document 1 discloses such a kneading degree adjusting apparatus. This kneading degree adjusting apparatus is provided with a cylindrical root diameter part (a cylindrical segment) formed in an intermediate part of a kneading screw in the axial direction. A gate member which is movable toward and away from the root diameter part is provided at a position of a barrel corresponding to this root diameter part in the axial direction.
When this gate member is moved toward the root diameter part, the area of a passage through which a material passes is reduced so that the material does not easily flow to the downstream side. Accordingly, the material remains in a kneading section so that the kneading degree is increased. When the gate member is moved away from the root diameter part (the cylindrical segment), the material easily flows so that the kneading degree of the material is decreased. That is, in the kneading degree adjusting apparatus of Patent Document 1, the material passage is opened and closed by the gate member thereby to adjust the kneading degree.
In recent years, in order to correspond to various compound resin materials, there is a strong demand for a wider adjusting range for the kneading degree than an adjusting range of a conventional kneading degree adjusting apparatus. In the conventional kneading degree adjusting apparatus, since an opening and closing range of the gate member is determined from a relationship with a barrel diameter, a lower limit of the kneading degree is not easily lowered. Therefore, in order to widen the adjusting range for the kneading degree, there is a need for raising an upper limit of the adjusting range for the kneading degree over that of the conventional kneading degree adjusting apparatus. Thus, the gate member is required to be movable closer to the cylindrical segment.
However, when the gate member is moved excessively close to the cylindrical segment in the kneading degree adjusting apparatus of Patent Document 1, there is a fear of metallic contacts between the gate member and the cylindrical segment. When the metallic contacts are caused, there are possibilities that the gate member and the cylindrical segment are abnormally worn away and the kneading quality is lowered due to contamination of seizure or the like. Therefore, in the kneading degree adjusting apparatus of Patent Document 1, the gate member cannot be moved closer to the cylindrical segment over the present predetermined distance, and hence the adjusting range for the kneading degree cannot be widened.    Patent Document 1: Japanese Utility Model Laid-Open No. 1993-72425